What is the factor here and with sites we own is content, huge information gathering and making its main info product free, this is what gets the traffic flow started. If there's little to search, you cant get the userbase, so no product for advertisers. Most B2bs fail on the content side, with only a few hundred or 1000 companies using it, the owners figure they don't need to put the effort in and I suppose when they realise no one signs up, they jack it in or let it slide, which is pointless for them as owners as I thought they were supposed to be providing a service for searchers? very strange....
If we are talking about the directory model, its still highly successful in/as niches eg: Alibaba, Myvouchercodes, and I believe it all re-started with Craigslist, I mean that sold for millions, quite a few took off media-wise such as Notgoingtouni, Monster-jobs again job directories etc etc, but the proof is here, it works as long as some cash is invested and its a labour of love - so the freebie model seriously works, so where do many go wrong?
Well, likely they rush for the cash too early, but before they have the full product and lack of promotion is a factor too for many. You must have sufficient content, or you wont get people returning to you... then you need sales/promotion, as we know that sales is the last thing that fits into place, traffic is the first thing that finds a site, so how to keep that returning is key. Do that and you got something to sell.
I think its unfair to label directories as non-credible resources, there;s still about 1500 that get good traffic, although these are B2b, and there are tiers/levels of success and limits to what they will deliver, again, a few factors at play here eg: traffic, age, amount of searchable content, niche, importance etc - but many are far more successful than the bad experiences/noise reveals.
The bad experiences are from disgruntled advertisers who likely jumped on board when their biz model was wrong for the site eg: they tried to take advantage of the freebie, when not thinking about the site being a good fit for their product.or service - there is a lot of this about, but its just noise and should be ignored.
Control of who signs-up is vital to success, keeping the undesirables out keeps the site clean and on track for commercialisation. I could show tons of success stories and failures, but that's another thread for another day, but staying true to the product is key before trying to pull in paying advertisers.